This invention relates to laser targets, and more particularly to electrically chargeable laser targets and method for forming such charged targets.
In certain magnetic confinement CTR systems, energetic neutral beams are injected and trapped by interaction with a target plasma. These target plasmas are generated by introducing into the confinement region a solid target or pellet of appropriate material which is vaporized and ionized by means of laser beams. This requires the capability to accurately guide the target to the desired focal spot. The standard way of accomplishing this task is to place an electrical charge on the target, whereby the trajectory can be influenced by standard electrostatic and/or magnetic means. Articles by C. D. Hendricks entitled "Charged Droplet Experiments", Journal of Colloid Science, vol. 17, No. 3, March 1962; and "Micron and Submicron Particle Production", IEEE Transactions On Industry Applications, Vol. 1A-10, No. 4, July/August 1974, pp. 508-510, exemplify prior known techniques in the forming of charged particles or targets. Also, the production of pellets using a fluid jet process is taught by J. M. Schneider et al., Rev. Sci. Inst. 35, 1349, 1964.
The ability to guide a target or pellet is directly related to the magnitude of the charge carried by a target. Accordingly, a target must have a relatively high electrical charge so as to be effectively guided or directed by guidance apparatus, such as that exemplified in U.S. Pat. No. 3,582,958 issued June 1, 1971 in the name of C. D. Hendricks, Jr.; and an article by J. R. Adam et al. entitled, "The Collision, Coalescence, and Disruption of Water Droplets", Journal of Applied Physics, Vol. 39, No. 11, 5173-5180, October, 1968. Thus, a need exists for a method of imparting a relatively high electrical charge upon a target and to do so without application of undue voltages which might produce breakdown of the atmosphere in the target-generating chamber, since the charge on the targets which can be achieved by prior known means is below the value required by electronic guidance systems for effective guidance off the targets.